In recent years, the use of a user terminal having both functions of cellular communication and wireless LAN (WLAN: Wireless Local Area Network) communication is increasingly becoming popular. Further, the number of WLAN access points managed by an operator of a cellular communication network increases. Therefore, in 3GPP (3rd Generation Partnership Project), a technology is being considered which is capable of strengthening cooperation (interworking) between a cellular RAN (Radio Access Network) and a WLAN (see Non Patent Literature 1).
On the other hand, an architecture of Dual Connectivity is being considered where an MeNB (Master eNodeB) that is a cellular base station configured to process data of a plurality of bearers passes the data of some bearers through an SeNB (Secondary eNodeB) that is another cellular base station (see Non Patent Literature 2).